The formation of calcium salt scales such as calcium phosphate, calcium oxalate, calcium carbonate, and calcium silicate, during liquid food processing is a significant problem for the food and beverage industry, particularly for breweries, vegetable juice processors, and evaporators in food processing plants. Exemplary liquid food streams that require processing include, but are not limited to: milk, whey, whey permeate, fruit and vegetable juices, calcium fortified beverages, sugar, corn wet milling steeping liquor, and fuel ethanol process streams from corn, sugar, or other biomass conversions. In particular, calcium phosphate may form during the processing of milk, and calcium oxalate may form during the processing of sugar, spinach, and other juices.
The formation of the calcium salt scales on processing equipment surfaces causes scaling or fouling, and decreases in the flow rate and the run-time. Various stages of food processing operations involve concentrating or heating liquid food process streams, such as during evaporation, filtration, or pasteurization. Typically, equipment scaling occurs during heat exchange stages, such as the evaporation stage and the ultra high temperature (UHT) stage of food processing operations. For example, during the UHT stage, the liquids are pasteurized at temperatures of around about 146 degrees Celsius as the liquid goes through the tube. The heat facilitates the formation and deposition of calcium salts on the surfaces of the equipment, decreasing the flow rate and run time of the equipment.
Current methods for removing calcium salts deposited on equipment surfaces typically involve using the alkaline salts of ethylene diamine triacetic acid (EDTA), biodegradable chelants, or strong solutions of nitric acid, phosphoric acid, or sulfuric acid. In the case of calcium oxalate deposits, hydrochloric acid and hydrofluoric acid may be used. These solutions dissolve the calcium salts and remove the scale, i.e., the calcium salt deposits, from the surface of the equipment. The equipment is cleaned daily with the calcium salts being removed during an acid rinse cycle.